Android Studio MPAndroidChart java.lang.NullPointerException: Attempt to invoke virtual method

Question

The 'findViewById' is in color red and cannot resolve method. What is wrong with my codes and what should I do?

This is the codes for my design in charts

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#f6f6f6"
    tools:context=".Charts">

    <TextView
        android:id="@+id/textView11"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:fontFamily="@font/montserrat"
        android:text="Distribution Chart"
        android:textColor="#242a2c"
        android:textSize="24dp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.github.mikephil.charting.charts.PieChart
        android:id="@+id/piechart"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="13dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView11">

    </com.github.mikephil.charting.charts.PieChart>



</android.support.constraint.ConstraintLayout>

This is my codes for the java file of my chart fragment

package com.example.admin.test2;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.github.mikephil.charting.charts.PieChart;
import com.github.mikephil.charting.data.PieData;
import com.github.mikephil.charting.data.PieDataSet;
import com.github.mikephil.charting.data.PieEntry;

import java.util.ArrayList;
import java.util.List;

public class Charts extends Fragment {

    float dataNum[] = {1000f, 500f, 150f, 50f, 6000f, 450f};
    String dataNames[] = {"Sample Data", "Sample Data", "Sample Data", "Sample Data", "Sample Data", "Sample Data"};

    public Charts() {
        setupPieChart();
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate (R.layout.fragment_charts, container, false);
    }

    private void setupPieChart()
    {
        //Populating a list of PieEntries;
        List<PieEntry> pieEntries = new ArrayList<> ();
        for (int i = 0; i < dataNum.length; i++)
        {
            pieEntries.add(new PieEntry(dataNum[i], dataNames[i]));
        }

        PieDataSet dataSet = new PieDataSet (pieEntries, "Sample Data");
        PieData data = new PieData (dataSet);

        //get the chart;
        PieChart chartt = (PieChart) findViewById(R.id.piechart);
        chartt.setData(data);
        chartt.invalidate();
    }
}

And this is the ERROR that I encountered

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.admin.test2, PID: 12568
                  java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.admin.test2/com.example.admin.test2.ScreenOne}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View com.github.mikephil.charting.charts.PieChart.findViewById(int)' on a null object reference
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2841)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
                      at android.app.ActivityThread.-wrap11(Unknown Source:0)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
                      at android.os.Handler.dispatchMessage(Handler.java:105)
                      at android.os.Looper.loop(Looper.java:164)
                      at android.app.ActivityThread.main(ActivityThread.java:6944)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View com.github.mikephil.charting.charts.PieChart.findViewById(int)' on a null object reference
                      at com.example.admin.test2.Charts.setupPieChart(Charts.java:49)
                      at com.example.admin.test2.Charts.<init>(Charts.java:24)
                      at com.example.admin.test2.ScreenOne.<init>(ScreenOne.java:32)
                      at java.lang.Class.newInstance(Native Method)
                      at android.app.Instrumentation.newActivity(Instrumentation.java:1180)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2831)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032) 
                      at android.app.ActivityThread.-wrap11(Unknown Source:0) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696) 
                      at android.os.Handler.dispatchMessage(Handler.java:105) 
                      at android.os.Looper.loop(Looper.java:164) 
                      at android.app.ActivityThread.main(ActivityThread.java:6944) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

I just want to display in the chart the data in the array.

score 0 · Answer 1 · answered Feb 02 '19 at 12:23

0

Create this method

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    setupPieChart();
}

And remove this

public Charts() {
      setupPieChart();
}

answered Feb 02 '19 at 12:23

Radesh

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is it okay? if it is a fragment... – user11005112 Feb 03 '19 at 03:03
It's ok I added it.. But why is my "findViewById" red though and it says cannot resolve method..??? – user11005112 Feb 03 '19 at 03:09
@user11005112 because still view not created, view create in onCreateView and you must do your work in onActivityCreated when use fragment – Radesh Feb 03 '19 at 13:15

Android Studio MPAndroidChart java.lang.NullPointerException: Attempt to invoke virtual method

1 Answers1